MICROCRYSTALLINE WAX AND PARAFFIN WAX
First draft prepared by
Dr K.B. Ekelman
US Food and Drug Administration
Washington DC, USA
1. EXPLANATION
Food-grade petroleum-derived hydrocarbon waxes were first
evaluated at the thirtieth meeting of the Committee (Annex 1,
reference 73). At that time, the Committee was informed that
toxicity data were available on certain hydrocarbon waxes, including
the results of long-term feeding studies in rats, but noted that
these studies were carried out with hydrocarbon waxes that had been
in commercial use in the 1960s. Because the Committee was not
informed whether the hydrocarbon waxes tested in these long-term
studies were equivalent to those currently produced by both
traditional and newer processes, no ADI was established.
At the thirty-third meeting (Annex 1, reference 83), the
Committee reiterated its need to be informed whether the chemical
composition of paraffin wax in current use met specifications for
this substance. It decided that for newer formulations of paraffin
wax, new specifications were required, and that adequate long-term,
mutagenicity, and reproduction/teratogenicity studies should be
completed (Annex 1, reference 83).
2. BIOLOGICAL DATA
2.1 Biochemical aspects
Some information about the metabolism of hydrocarbon oils was
briefly reviewed by Freeman and co-workers (1989): Studies indicate
that normal, branched and cyclic paraffins are absorbed from the
mammalian gastrointestinal tract and that the absorption of
n-paraffins is inversely proportional to the carbon chain length,
with little absorption above C30. With respect to the carbon chain
lengths likely to be present in mineral oil, n-paraffins may be
absorbed to a greater extent that iso- or cyclo-paraffins.
In a recent review of hydrocarbon intestinal absorption and
metabolism, Barrowman and co-workers (1989) stated that
representatives of the major classes of hydrocarbons have been shown
to be well absorbed by the gastrointestinal tract in various
species. In many cases, the hydrophobic hydrocarbons are ingested in
association with dietary lipids. Authors reviewed the dependence of
hydrocarbon absorption on concomitant triglyceride digestion and
absorption, and discussed the "hydrocarbon continuum" hypothesis,
which asserts that a series of solubilizing phases in the intestinal
lumen, created by dietary triglycerides and their digestion
products, afford hydrocarbons a route to the lipid phase of the
enterocyte membrane.
While some hydrocarbons may traverse the mucosal epithelium
unmetabolized and appear as solutes in lipoprotein particles in
intestinal lymph, there is evidence that most hydrocarbons partially
separate from nutrient lipids and undergo metabolic transformation
in the enterocyte. Thus, Barrowman and co-workers (1989) concluded
that the enterocyte may play a major role in determining the
proportion of an absorbed hydrocarbon that, by escaping initial
biotransformation, becomes available for deposition in its unchanged
form in peripheral tissues such as adipose tissue, or in the liver.
Barrowman and co-workers (1989) also summarized information on
the solubility of various hydrocarbons in liquid trioleoyl glycerol;
information in the following table is taken from Table 1 of their
review:
Table 1: Solubility of Various Hydrocarbons in Liquid Trioleoyl Glycerol
Solubility Temperature
Hydrocarbon (g solute/100 g fat) (° C)
Octadecane 9.26 14
82.69 27
Eicosane 4.02 14
9.55 27
Docosane 0.60 14
2.12 27
12.69 37
Results of extraction and migration tests that have been
performed on waxes and wax-bearing products, however, indicate that
hydrocarbon waxes consumed in the diet are unlikely to be absorbed
or metabolized in detectable or significant amounts (Eldred, 1990;
Eldred & Modderman, 1990; European Wax Federation, 1990; Kelly &
Castle, 1989; Orfan, 1990; Orfan & Bonica, 1989; van Battum & Rijk,
1979; van den Berg, 1990; van den Berg et al., 1989; and Woldhuis
& Kemp, 1989). For example, gum base waxes do not leach into saliva
at a detection limit of 1 mg/kg and hydrocarbons are not extractable
by gastric and pancreatic fluids at a detection limit of 0.5 mg/kg.
On the basis of information about the physical characteristics
of oils and waxes and the results of extraction and migration tests
that have been performed on waxes and wax-bearing products, Arnold
(1991) argues that hydrocarbon waxes are less likely to be toxic
than hydrocarbon oils because:
1) they cannot be readily dispersed as emulsions at body
temperatures, and
2) migration tendencies and solubility in most media is minimal or
zero.
Both conclusions are based on the fact that waxes generally consist
of longer-chain hydrocarbons than the hydrocarbons in oils and,
thus, are solids at ambient and body temperatures.
A recent description of the accumulation of long-chain alkanes
(C29, C31, and C33) in a patient who had died of heart disease
led the author to conclude that these hydrocarbons were of dietary
(plant) origin as judged by the tissue distribution of the alkanes
(Salvayre et al., 1988).
2.2 Toxicological studies
2.2.2 Short-term studies
No information available.
2.2.3 Long term/carcinogenicity studies
Groups of fifty 6-8 week old male and female Sprague-Dawley
rats were fed diets containing 10% ground wax (petrolatum; 5
samples) for two years. In addition, 157 female and 140 male rats
served as untreated controls. Waxes were chosen to represent the
range of polycyclic aromatic hydrogen content of waxes in commercial
use (0-0.64 ppm). The rats were observed and weighed every other
week, and all gross lesions were recorded. Rats were observed until
spontaneous death or were killed in extremis; necropsies were
performed on all animals and histologic examination was performed on
all abnormal tissues. Survival rates and average weights of
experimental groups did not differ significantly from those of
control animals, and the incidence of tumours observed in
experimental animals was consistently similar to incidences of these
tumours in control animals. No other wax-associated toxic effects
were identified by histopathology (Shubik et al., 1962). Recent
personal communications from two of the authors of this study
(Shubik and Saffiotti) confirm that findings in recent 90-day
studies on mineral oils - deposition in the reticuloendothelial
system and granulomas in the livers of rats - were not observed in
the two-year oral toxicity study of waxes in rats.
Shubik and co-workers (1962) also reported that five petrolatum
waxes were negative for local and systemic carcinogenicity or
toxicity in skin painting studies in mice and rabbits (applied 3
times each week until death of the animals), and that wax disk
implants, but not ground wax implants, were associated with the
development of fibrosarcomas at the implantation site. Neither of
the studies is directly relevant to determining the likely effects
of ingestion of hydrocarbon waxes.
A series of 180-day rat feeding studies were performed over a
period of approximately 15 years (beginning in 1955) on chewing gum
bases containing a hydrocarbon wax at proportions varying from 2 to
57% of the gum base. In total, there were 16 series of control rats
(120 males and 120 females) and 27 series of experimental animals
(186 males and 195 females). Male and female rats were 4 weeks old
at the beginning of the studies. Calculated feeding levels for the
waxes were reported to vary from 0.16% to 4.75% of the diet. Test
animals were fed diets consisting of 75% basal diet, 8.3% gum base,
and 16.67% wood flour. Endpoints measured included body weight, food
consumption, urinalysis, gross pathology and histopathology (organs
examined were the heart, liver, spleen, adrenal, gonad, kidney,
small intestine and large intestine). A total of 78 control rats and
109 experimental rats from these studies were maintained up to
19 months of age following the conclusion of the feeding study;
these animals were examined for late-occurring pathologic changes
that may be associated with the test compound.
A summary report of these studies noted that an influenza
epidemic in the animal colony in the first part of 1957 increased
the number of intercurrent deaths and pulmonary lesions in test
animals. The following non-significant findings were described: (1)
3/120 control males and 7/186 test males demonstrated impaired
testicular function (decreased spermatogenesis, reduced testicular
weight, or both); (2) malignant tumours were found in 5/241 controls
and 4/381 experimental rats; and (3) haemorrhagic manifestations,
usually in association with pulmonary lesions, and prolonged
prothrombin times were reported for 4/241 controls and 5/381
experimental rats (particularly during the pneumonia epidemic noted
above). For the complete set of experiments, and for those
experiments in which hydrocarbon wax was a high percentage of the
chewing gum base, the authors reported that no compound-related
effects were observed (Davidsohn & Stern, 1960; Wrigley Co., 1959).
3. COMMENTS
At the present meeting, the Committee concluded that waxes
tested in previous studies contained a broader spectrum of waxes
than those in use today; two specifications for food-grade
petroleum-derived hydrocarbon waxes were prepared (paraffin wax and
microcrystalline wax. Because these specifications limit the number
of waxes that can be used for food applications as compared with
those tested in previous studies, the Committee concluded that
previous long-term toxicity studies were suitable for evaluating the
safety of hydrocarbon waxes in current use. Additional long-term and
mutagenicity studies on paraffin wax and microcrystalline wax were
therefore not required. The results of extraction and migration
tests performed on waxes or wax-bearing products indicated that
hydrocarbon waxes consumed in the diet are not absorbed or
metabolized in significant amounts.
In a long-term feeding study with Sprague-Dawley rats, no
wax-related effects were observed. In a series of 180-day feeding
studies in rats that were performed over a period of approximately
15 years (beginning in 1955) on chewing-gum bases containing
hydrocarbon wax in proportions varying from 2% to 57% of the gum
base, no compound-related effects were observed.
Five petrolatum waxes were negative for local and systemic
carcinogenicity or toxicity in skin-painting studies in mice and
rabbits. However, wax disk implants, but not ground wax implants,
were associated with the development of fibrosarcomas at the
implantation site in rats.
4. EVALUATION
Because long-term toxicity studies indicated that
petroleum-derived paraffin and microcrystalline waxes are non-toxic
and non-carcinogenic, the Committee established a group ADI "not
specified" for microcrystalline wax and paraffin wax for the uses
indicated in the specifications (chewing-gum base, protective
coating, defoaming agent, and surface finishing agent).
The Committee was informed that a 90-day study on hydrocarbon
waxes made both by newer processes and by traditional methods was
under way, and asked to be informed of the results when they became
available.
5. REFERENCES
ARNOLD, F.V. (1991) Reasons to differentiate fully refined petroleum
waxes from white oils. European Wax Federation.
BARROWMAN, J.A., RAHMAN, A., LINDSTROM, M.B., & BORGSTRON, B. (1989)
Intestinal absorption and metabolism of hydrocarbons. Prog. Lipid Res., 28: 189-203.
DAVIDSOHN, I. & STERN, K. (1960). Letter to J.I. Weeks.
ELDRED, J.S. (1990) Letter to D. Lees. Keller and Heckman,
Washington, DC.
ELDRED, J.S. & MODDERMAN, J.P. (1990) Letter to D. Lees. Keller and
Heckman, Washington, DC.
EUROPEAN WAX FEDERATION (1990) Specifications for petroleum derived
hydrocarbon waxes - Food grade (Petroleum Waxes E905c).
FREEMAN, J.J., BILES, R.W., CRAGIN, D.W., McKEE, R.H., NIKIFOROV,
A.I. & SMITH, J.H. (1989) Liquid mineral hydrocarbons in food:
Review of current issues, EXXON Corporation's toxicological data,
and consideration of potential human health effects. EXXON
Biomedical Sciences, Inc. Technical Report, East Millstone, NJ.
KELLY, M. & CASTLE, L. (1989) Mineral hydrocarbons levels in waxed
cheese and in skinless sausages. FScL Internal Report 89/28.
ORFAN, C.P. (1990) Laboratory Report 7b, 13b: Hydrocarbon extraction
of paraffin wax and microcrystalline wax in gum base and finished
gum, alone and when combined with cocoa butter and/or chocolate, by
simulated saliva, gastric, and intestinal fluids. L.A. Dreyfus
Company.
ORFAN, C.P. & BONICA, V.C. (1989) Laboratory Report 7b, 13b:
Hydro-carbon extraction in gum base and finished gum by synthetic
gastric and intestinal fluids. L.A. Dreyfus Company.
RUSTIGE, J. (1991) Letter to J.L Herrman. European Wax Federation.
SALVAYRE, R., NEGRE, A., ROCCHICCIOLI, F., DUBOUCHER, C., MARAT, A.,
VIEU, C., LAGARON, A., POLONOVSKI, J. & DOUSTE-BLAZY, L. (1988). A
new human pathology with visceral accumulation of long-chain
n-alkanes; tissue distribution of the stored compounds and
pathophysiological hypotheses. J. Biochim. Biophys. Acta, 958:
477-483.
SHUBIK, P. ET AL. (1962). Studies on the toxicity of petroleum
waxes. Tox. and Appl. Pharm., 1-62.
SIMPSON, B. (1990) Draft protocol for 90-day feeding study with
mineral hydrocarbons. The oil companies' European organization for
environmental and health protection (CONCAWE), Brussels, Belgium.
VAN BATTUM, D. & RIJK, M.A.H. (1979) Report B77/2694A: Migration
experiments with waxed papers; Fifth report; Results obtained with
various foodstuffs. Central Institute for Nutrition and Food
Research (TNO)
VAN DEN BERG, G. (1990) Is there any significant migration of wax
into cheese? NIZO-EDE.
VAN DEN BERG, G., OLIEMAN, C. & VAN RIEL, J. (1989) Investigation of
the possible migration of wax components into cheese. NIZO-EDE.
WHITE PAPER: Mineral hydrocarbon waxes used in chewing gum. Prepared
for possible presentation by EACGI or CAOBISCO to the European
Community's Scientific Committee for Food and to Commission staff.
Anonymous, undated.
WOLDHUIS, J. & KEMP, G. (1989) Hydrocarbon content of cheese rind by
comparative GPC and GC analysis. European Wax Federation, Brussels,
Belgium.
Wm WRIGLEY Jr. COMPANY (1959). Report on toxicity tests; ingredients
used in the manufacture of the Wrigley brands of chewing gum;
history and complete data (1959).